Former Virginia governor Robert F. McDonnell (R) at his sentencing last year. (Jay Westcott/REUTERS)

If the Supreme Court overturns the convictions of former Virginia governor Robert F. McDonnell, the decision could substantially narrow what is considered criminal public corruption and put the brakes on investigations of allegedly unscrupulous politicians across the country, experts said.

Attorneys for former Illinois governor Rod Blagojevich (D) and former New York Assembly speaker Sheldon Silver (D) — both convicted in corruption cases that are still making their way through the court system — said they are watching McDonnell’s case closely, cognizant that the Supreme Court’s decision might help their clients. Experts said the fates of other politicians charged or convicted of public corruption — including Sen. Robert Menendez (D-N.J.) and Dean Skelos (R), former New York state Senate majority leader — might also be affected.

The McDonnell case strikes at the core issue of when, and to what extent, money should be allowed to influence politics. The high court is essentially being asked to clarify the line between a public official legally performing a routine courtesy for a benefactor and a politician corruptly using government power in exchange for a bribe.

“If it’s a reversal, it’s going to make it more difficult for these cases in the future,” said Randall Eliason, a former federal prosecutor specializing in public corruption and government fraud. “But the devil’s in the details. It’s going to boil down to how they reverse and what exactly they say.”

An attorney for McDonnell and a spokesman for the prosecutors who handled the case declined to comment for this report.

On this much, most agree: That the Supreme Court took McDonnell’s case means a good number of the justices think that U.S. public corruption law is worth examining.

McDonnell and his wife, Maureen, were convicted in September 2014 of lending the prestige of the governor’s office to Richmond businessman Jonnie R. Williams Sr. in exchange for $177,000 in loans, vacations and luxurious gifts. The former Republican governor was sentenced to two years in prison, his wife to a year and a day. Both appealed their convictions and were allowed to stay out of prison with those challenges pending.

Robert McDonnell’s case was the first to arrive at the Supreme Court, which agreed earlier this month to hear the matter, and his wife’s has been put on hold. The former governor’s attorneys have argued that what he did — or tried to do — for Williams did not constitute an “official act,” and he thus could not be found guilty of public corruption. They asserted that his conviction, if allowed to stand, would make criminals out of virtually every politician and give prosecutors unchecked authority to decide which ones to target.

The U.S. solicitor general fired back that McDonnell’s case was a routine example of an official taking personal benefits to influence government matters, and the evidence at the trial “amply supported” his conviction. Prosecutors had alleged he used the power of his office by arranging meetings for Williams with other state officials, allowing Williams to use the governor’s mansion for a luncheon on the day his product, a dietary supplement called Anatabloc, was being launched and personally touting the supplement to state human resources officials. That was part of a broader effort, prosecutors alleged, to have Anatabloc studied by state researchers or included in the state’s health plan.

The supplement was never studied or offered as part of the health plan, and defense attorneys contended the other acts were routine political courtesies in no way tied to Williams’s largesse.

List of gifts given to the McDonnell family from Jonnie Williams.

The case comes before the Supreme Court at a time when presidential candidates from both parties are turning a critical eye to the pervasive influence of money in politics. Republican businessman Donald Trump, notably, has said he believes his donations have won him favors from politicians.

Eliason, who wrote a blog post arguing that the Supreme Court should not take McDonnell’s case, said although it is true that “people provide monetary support to politicians all the time, and politicians do things that their supporters favor all the time,” he thought McDonnell’s case was different in that prosecutors had demonstrated a corrupt agreement. He said the Supreme Court could leave federal prosecutors with far less latitude to pursue politicians whom they suspect of selling their offices — either by requiring prosecutors to provide even more evidence to demonstrate such an agreement or narrowing what is considered an “official act.”

Many say that is necessary, and that the former governor’s conviction gives law enforcement officials the ability to go after any politician in America. Eleven groups filed amicus briefs supporting McDonnell’s bid to have the high court review his case, among them 66 former state attorneys general, 31 governors and a collection of former high-ranking federal officials, including a retired judge.

But others say they fear the Supreme Court will further weaken U.S. public corruption laws, which have already been restricted by previous court rulings.

“It speaks volumes that we’re pushing other countries to ramp up their anti-corruption efforts and here in the U.S. potentially loosening our efforts when it comes to our own officials,” said Jessica Tillipman, an assistant dean of George Washington University Law School who teaches an anti-corruption seminar.

The high court could uphold McDonnell’s conviction or rule in a way that would have limited impact — perhaps taking a nuanced view of why a jury instruction was in error. But lawyers and politicians across the country are watching the case, many expecting more.

Steven Molo, an attorney for Silver, said he is among those waiting for the McDonnell decision, which could affect his client’s case. Silver, accused of using his position to influence real estate legislation and state funding in exchange for millions of dollars in bribes and kickbacks, was convicted of corruption in November. He is awaiting sentencing.

“Our case involved many of the same issues, so it certainly could have an impact,” Molo said.

Len Goodman, an attorney for Blagojevich, said he is hopeful that the Supreme Court’s interest in McDonnell’s case signals that the justices might also be interested in his client’s. Blagojevich, Goodman said, also has petitioned to have the Supreme Court hear his case. He said the McDonnell and Blagojevich cases both “involve the scope of the criminal extortion statue,” although the issues are slightly different.

Blagojevich, who was convicted on corruption charges related to attempting to sell President Obama’s Senate seat, is “not questioning that what he did was an official act,” Goodman said. Rather, he is contesting that there was a connection between what he did and the campaign contributions prosecutors say he sought in return.

“There was no explicit promise,” Goodman said. “That’s why the case is so important, that the Supreme Court clarifies, ‘What is the rule?’ If the politician is on the phone asking people for money and they know that person has an issue before them, is that lawful?”

Experts said Menendez, also charged in a corruption case, and Skelos, who was convicted on corruption charges last month, are also probably looking to a decision on McDonnell for help, though the facts of each case are slightly different. Attorneys for Menendez and Skelos declined to comment for this report.

Kelly Kramer, a white-collar criminal defense attorney at the Mayer Brown firm, said the Supreme Court has scaled back the “honest services fraud” statute, as it is called, in deciding the case of former Enron executive Jeffrey Skilling, limiting such prosecutions to cases involving bribes or kickbacks, rather than mere self-dealing.

Although Kramer said it is possible the Supreme Court’s decision on McDonnell could be limited to the notion of official acts, he said the justices might offer more sweeping guidance on the interplay between honest services fraud, the federal bribery statute and state and local regulations.

Barak Cohen, a former federal prosecutor who does white-collar defense work at Perkins Coie, said what constitutes an official act is undeniably “muddy,” and prosecutors and defense attorneys across the country are looking to the Supreme Court for guidance. But Cohen said even if the justices significantly narrow the definition, politicians probably will not see that as a license to push the envelope.

“I don’t think any politician wants to be exposed as doing the things Bob McDonnell did,” Cohen said. “It doesn’t matter if it’s a crime or not.”